( m to undergo an acrosome reaction. This...)Environmental chemical cocktail may sabotage sperm

m to undergo an acrosome reaction. This is when the cap on the head of the sperm ruptures and releases enzymes that enable the sperm to penetrate the coverings of the egg. If the acrosome reaction happens before a sperm reaches the egg, then fertilisation is unable to take place because the sperm has lost special "docking" molecules that allow it to bind to the egg.

Prof Fraser said: "Human sperm proved to be even more responsive than mouse sperm to genistein. These compounds are classified as environmental oestrogens, but they are very weak, so normally you would expect them to have to be in concentrations around 1,000 times stronger to get a response similar to that prompted by the naturally occurring oestrogen, oestradiol. Yet human sperm are responding to very low concentrations ?well within the amounts that have been measured in people's blood.

"At a time when there are concerns that the incidence of infertility may be rising, this research flags up important warning signs. Very little is currently known about the control of sperm function, especially in the body rather than in the laboratory, but the sensitivity of human sperm to these chemicals means that further investigations should be carried out to determine whether such environmental compounds might contribute to a decrease in human fertility. Other scientists have investigated the negative impact of environmental chemicals on testis function, resulting in reduced numbers of sperm being produced, but these effects require much larger doses than we have used. As far as I am aware, we are the only group looking at subtle effects that could have a serious impact on fertility without reducing the number of sperm being produced."

The mechanism of action of the environmental oestrogens was still not clear, but the researchers discovered that both genistein and nonylphenol significantly stimulated the production of cyclic AMP ?a chemical messenger, produced within the cell after external
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Source:European Society for Human Reproduction and Embryology

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